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Full text of "Abnormalities in the Chick Embryo"

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476 



SCIENCE 



[N. S. Vol. XL VIII. No. 1245 



The device affords a simple means of illus- 
trating the chaotic movement of a large num- 
ber of small particles similar to the motion of 
molecules in gases and vapors. The similarity 
is especially instructive when compared with 
the evaporation of a liquid since the effect of 
the evaporating mercury upon the particles 
leaving its surface is similar to the actual 
motion, of vapor molecules which leave a 
liquid. 

The phenomenon can be projected upon a 
screen and the particles and their movement 
greatly magnified, so that the device may be 
used for lecture demonstration of the kinetic 
theory. 

E. E. Stoekle 
Physical Laboratory, 
The Cutler-Hammer Mfg., Company 

ABNORMALITIES IN THE CHICK EMBRYOl 

For the past five years the writer has had 
under her supervision the preparation of the 
vast amount of material used for large em- 
bryology classes. On account of the possibly 
controlled conditions under which it could be 
obtained, the chick was extensively used. Hun- 
dreds of these embryos have been examined. 
Seldom were the eggs incubated for a longer 
period than three days. For the first two 
years the pressure to secure material was so 
great than only the normal embryos of the 
right degree of development were saved. It 
was noticed that a large per cent, of the fertile 
eggs did not give embryos which were satis- 
factory for class use. The obtaining of an ex- 
tremely abnormal embryo and two embryos on 
one blastoderm in a single incubation lead to 
the saving of all of the specimens. Since that 
time, over two hundred abnormal ones have 
been collected. 

The abnormalities seemed to occur more in 
the central nervous system than elsewhere. 
Two regions were particularly affected, the 
brain and the neural tube in the region of the 
last two or three mesoblastic somites and the 
beginning of the segmental plate. However, 
the abnormalities did not occur in both of 

i Contribution from the Zoologieal Laboratory, 
Kansas State Agricultural College, No. 22. 



these regions in the same embryo. In embryos 
obtained from eggs incubated forty-eight hours 
the abnormality of the neural tube extended 
over a length of between one eighth and one 
fourth of a millimeter. The neural tube here 
was either solid without a central canal or the 
central canal was extremely small, or there 
were from two to five canals. This could be 
recognized in the whole mount as apparent 
loops of one side of the neural plate, or as a 
thickened part of the entire tube. The most 
extreme case of the abnormality of the brain 
was a seventy-two-hour chick, in which the 
brain was only about one-fourth the normal 
size and the fore-, mid- and hind-brains ap- 
peared as a series of loops. Another example 
was a forty-eight-hour chick which had an 
optic vesicle less than one third the normal 
size. This optic vesicle was connected with 
the brain by a stalk more than twice the nor- 
mal length. 

During the past summer Miss Alsop, a grad- 
uate student, undertook some experiments 
upon the cause of these abnormalities. At 
the same time we were running some controls 
under normal conditions. She found that she 
could obtain a large per cent, of abnormalities, 
and, at will, could produce them either in the 
brain region or in the region of the tube. She 
hopes to have a detailed account of her ex- 
periments, along with drawings and a more 
extended description of these abnormalities, 
ready for publication in a short time. 

Mary T. Heaman 
Kansas Agricultural College, 
Manhattan, Kans. 



SCIENCE 



A Weekly Journal devoted to the Advancement of 
Science, publishing the official notices and pro- 
ceedings of the American Association for 
the Advancement of Science 

Published every Friday by 

THE SCIENCE PRESS 

LANCASTER, PA. GARRISON, N. Y. 

NEW YORK, N. Y. 

Entered in the post-office at Lancaster, Pa., as second class matter